Multiple ply lamented embossed paper products are typically of two types, "nested" and "pillowed", each of which have substantially greater bulk than non-embossed multiple ply products. When a tissue or towel sheet is provided with an embossed pattern, projecting raised areas and recessed areas are produced corresponding to the protuberances and recessed areas of the embossing rolls. A "nested" product results when projecting raised areas of a first web are aligned with the recessed areas between two raised areas of a second web, whereas a "pillowed" sheet results when projecting raised areas of both first and second webs are placed adjacent one another with the recessed areas of the two sheets creating a relatively large void between adjacent raised areas.
The primary problem associated with multi-ply embossed paper webs is that, traditionally, the plies have been combined at the nip between the steel embossing rolls. This metal-to-metal contact at the embossing roll nip has resulted in excess wear of the embossing rolls requiring frequent and costly repair or replacement of the rolls. This problem was recognized in U.S. Pat. No. 3,867,225 issued to Nystrand wherein the plies are combined between one of the steel embossing rolls and a rubber-covered "marrying roll" which permits the nip between the two embossing rolls to be run open, thereby reducing wear on and extending greatly the useful life of the embossing rolls.
However, the process set forth in the above-noted patent to Nystrand, is useful only for producing a "nested" type product since the solid surface marrying roll would substantially debulk a pillowed product. A pillowed multi-ply product is shown in U.S. Pat. No. 3,738,905 issued to Thomas, however, this method suffers from the aforementioned embossing roll wear problem at the combiner nip. A solid surface marrying roll, as disclosed in the Nystrand patent utilized with this process would result in approximately fifty percent of the lamented bulk sheet being removed during the embossing stage.
In an effort to overcome the aforementioned shortcomings, a relief pattern marrying roll is set forth in U.S. Pat. No. 4,483,728 issued to Bauernfeind wherein a marrying roll especially adapted to combine multiple plies of a tissue sheet at a nip between the marrying roll and an embossing roll is set forth. The marrying roll is provided with a pattern of raised lamented elements covering a predetermined percentage of the marrying roll surface which are caused to bear against the raised embossing elements of an embossing roll with the plies of a pillowed tissue sheet therebetween. The pattern of raised elements on the marrying roll surface may be in the form of dots, a rectangular grid pattern, or any other pattern of choice. The pattern is preferably aligned at an angle to the machine direction to eliminate bunching or puckering of the tissue sheet between pattern elements. During the manufacture of the multi-ply web, adhesive is applied to the projecting raised areas of one of the plies; however, the embossed webs are related with one another but not joined at an open nip between the embossing rollers in that the adhesive which has been applied is insufficient to laminate the webs together because the nip between the embossing rolls is run in the open position to prevent embossing roll damage often experienced in such systems. It is the marrying roll which presses the plies together to adhered such plies to one another which forms the two-ply web. In this regard, the embossing rolls are inadequate to adhere the single ply webs to one another and the use of marrying roll results in a decrease in the lamented sheet bulk.
U.S. Pat. No. 5,215,617 issued to Grupe sets forth yet another method of forming multi-ply webs wherein matched rubber and embossing rolls are used to reduce strength degradation of the ply during embossing and to permit the use of rotogravure adhesive printing when forming nested webs. That is, matched embossing roll pairs are used to emboss separate paper plies which are subsequently adhered to one another by adjacent rolls of each of the pair of embossing rolls. When forming the nested ply, one of the embossing rolls includes a rubber covered roll having embossing elements which permits the use of rotogravure adhesive printing. However, this reference fails to recognize the formation of a pillow type multi-ply web wherein the plies are adhered to one another at the nip formed between adjacent embossing rolls. Further, applying the adhesive to the raised portions of the soft rubber roll may result in a reduction in the effectiveness of the spot bonding between plies which results in stiffening of the two-ply web.
Therefore, there is a need for an embossing roll arrangement which will permit the embossing of pillowed type multi-ply webs without debulking the web in any manner. Moreover, there is the need for a method of producing a multi-ply soft absorbent web while eliminating the use of a marrying roll which inherently reduces the overall bulk of the multi-ply web. Moreover, there is a need for a method of forming pillow type multi-ply webs having equal emboss definition on both sides thereof and which is not unduly stiffened by the application of adhesives.